1. Field of the Invention
This invention relates to oil and gas well completion and production.
2. Description of the Prior Art
Geologists have known for years that substantial deposits of oil and natural gas are trapped in deep shale formations. Around the world today, with modern horizontal drilling techniques and hydraulic fracturing, the trapped oil and natural gas in these shale reservoirs is being produced, gathered and distributed to customers.
Initially, a vertical hole is drilled in a formation down to a depth below the water table, and steel casing is inserted into the borehole and cemented in place, thus providing an impermeable barrier between the water table and borehole. Vertical drilling continues to a depth called the “kick-off” point, where the wellbore begins curving to become horizontal. One advantage of horizontal drilling is that it is possible to drill several wells from only one drilling pad, minimizing the impact to the surface environment. When the targeted distance is reached, the drill pipe is removed from the borehole, and additional steel casing is inserted through the full length of the wellbore and cemented in place.
The drilling rig is then removed and preparations for well completion are then undertaken. The first step is to create a connection between the final casing and the reservoir rock. To do so, a device known as a perforating gun, equipped with shaped explosive charges, is lowered into the wellbore down to the layer containing oil and/or natural gas. The perforating gun is then fired, which creates holes through the casing, cement, and into the target reservoir rock. Next, a mixture of water, sand and other chemicals is pumped into the deep underground reservoir formations, which creates fractures in the reservoir rock. A propping agent, usually sand carried by the high viscosity fluid, is pumped into the fractures to keep them from closing when the pumping pressure is released. This initial stimulation segment is then isolated with a specially designed plug inserted into the steel casing to seal off the perforated (and thus the fractured reservoir) and prevent production from the isolated section. The perforating gun is then moved to the next stage of the wellbore to perform the same process, which is then hydraulically fractured in the same manner. This process is repeated along the entire horizontal section of the well, which may extend several miles.
Once the stimulation is complete, the isolation plugs are drilled out and production begins. Initially water, and then natural gas or oil flows into the horizontal casing and up the wellbore. In the course of initial production of the well, approximately 15 to 50% of the fracturing fluid may be recovered, a process known as “flowback.” The purpose of the flowback is to safely recover these substances from the well and transition the marketable hydrocarbons of the well stream to a sales pipeline or storage tank. The fracturing fluid is then either recycled to be used on other fracturing operations or safely disposed of according to government regulations.
The fracturing process described above requires equipment to handle and separate drilled isolation plug cuttings along with large volumes of sand, fracturing fluids, and oil and natural gas. The drilled isolation plug cuttings and sand need to be separated to keep from plugging other fluid clean up and separation equipment, which may cause a loss of circulation detrimental to downhole tools. Accordingly, a device is needed to efficiently separate drilled isolation plug cuttings, sand, fracturing fluids and oil and natural gas during a flowback process of production of fluids from the wellbore.
3. Identification of the Objects of the Invention
An object of the invention is to accomplish one or more of the following:
Provide an apparatus for primary separation in fracking operations that combines isolation plug cutting separation, sand separation, and gas separation in a single separation assembly.